Thyroid
TSH Levels: What's Normal and What High or Low TSH Means
TSH (thyroid-stimulating hormone) tells you how hard your body is signalling the thyroid gland. It's the main screen for thyroid problems, which are common — particularly in women.
Normal TSH (Thyroid) range
What a high TSH (Thyroid) means
A high TSH usually means an underactive thyroid (hypothyroidism) — the body is signalling harder because thyroid hormone is low. Symptoms can include tiredness, weight gain, feeling cold, dry skin and low mood.
Common causes:
- Hypothyroidism (often autoimmune)
- Iodine imbalance
- Some medicines
- After thyroid treatment
What a low TSH (Thyroid) means
A low TSH often means an overactive thyroid (hyperthyroidism). Symptoms can include weight loss, fast heartbeat, anxiety, tremor and feeling hot.
- Hyperthyroidism
- Over-treatment with thyroid medicine
- Thyroid nodules
Food & lifestyle that help
Favour
- A balanced diet with iodine (iodised salt)
- Fruits, vegetables and whole grains
- Adequate protein
Limit
- Self-prescribed iodine or thyroid supplements
- Highly processed food
When to see a doctor
TSH should be interpreted by a doctor, often with T3/T4, before starting or changing any thyroid medicine — dosing needs to be individualised.
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Make my free plan →Frequently asked questions
What is a normal TSH level?
Roughly 0.4–4.0 mIU/L for most adults, but ranges differ by lab and in pregnancy.
Is high TSH serious?
High TSH points to an underactive thyroid, which is very treatable with medication once confirmed and monitored by a doctor.